Butterfly valve method and apparatus

Abstract

A method for exploiting the net torque exerted by a conveyed fluid on the valve plate of a butterfly valve to facilitate control of the valve, and a butterfly valve (40) adapted for use with the method are disclosed. The method employs translational movement of the valve plate to facilitate rotational movement of the same and to effect dynamic torque balancing. The butterfly valve (40) employs a differential gear (50) as a mechanical resolver to produce either rotational or translational components of movement depending on whether the net torque exerted by the fluid is sufficiently high to overcome impedance to translational movement.

What is claimed is: 
     
       1. A butterfly valve, comprising: a mounting body defining a portion of a flow path for a fluid to be conveyed therethrough;   a valve plate supported within and transecting the flow path;   pivot means journalled in the mounting body for supporting the valve plate; the valve plate being pivotable with the pivot means and translatable relative thereto;   a differential gear operably connected to the pivot means to transmit torque thereto; and   an input shaft operably connected to the differential gear to apply input torque to the latter.   
     
     
       2. The invention of claim 1 wherein the valve is operable to rotationally move the valve plate in response to the input torque when the rotational movement is insufficiently impeded, and to translationally move the valve plate relative to the pivot means when the rotational movement is sufficiently impeded. 
     
     
       3. The invention of claim 1 wherein the valve is operable to translationally move the valve plate relative to the pivot means in response to the input torque when the translational movement is insufficiently impeded, and to rotationally move the valve plate in response to the input torque when the translational movement is sufficiently impeded. 
     
     
       4. The invention of claim 2 further comprising biasing means for impeding translational movement of the valve plate relative to the pivot means. 
     
     
       5. The invention of claim 4 wherein the biasing means comprises a spring interposed between the valve plate and the pivot means. 
     
     
       6. The invention of claim 1 further comprising bearing means for minimizing friction between the valve plate and the pivot means during translational movement of the former relative to the latter. 
     
     
       7. The invention of claim 6 wherein the pivot means comprises a carrier journalled in the mounting body and a center shaft journalled in the carrier; the center shaft and carrier being operably connected to the differential gear whereby, in response to rotation of the input shaft, the differential gear is operative to transmit torque to the center shaft and is operative to rotate the carrier when the center shaft is constrained from rotating. 
     
     
       8. The invention of claim 1 wherein the pivot means comprises a carrier journalled in the mounting body and a center shaft journalled in the carrier; the center shaft and carrier being operably connected to the differential gear whereby, in response to rotation of the input shaft, the differential gear is operative to transmit torque to the center shaft and is operative to rotate the carrier when the center shaft is constrained from rotating. 
     
     
       9. The invention of claim 8 further comprising biasing means for impeding translational movement of the valve plate relative to the carrier. 
     
     
       10. The invention of claim 8 further comprising a rack gear rigidly secured to the valve plate, and a pinion gear rigidly secured to the center shaft and extending through the carrier to engage the rack gear; the rack and pinion gears being operative in response to rotation of the center shaft to translate the valve plate relative to the pivot means. 
     
     
       11. The invention of claim 10 further comprising bearing means for minimizing friction between the valve plate and the carrier during translational movement of the former relative to the latter. 
     
     
       12. The invention of claim 10 further comprising biasing means for impeding translational movement of the valve plate relative to the pivot means. 
     
     
       13. The invention of claim 12 wherein the biasing means comprises a spring interposed between the carrier and the valve plate. 
     
     
       14. The invention of claim 13 further comprising bearing means for minimizing friction between the valve plate and the carrier during the translational movement. 
     
     
       15. The invention of claim 1 wherein the valve plate is translatable relative to the pivot means in a direction substantially coextensive with the former whereby in operation, the butterfly valve is operable to alter net fluid dynamic torque exerted by the fluid on the valve plate. 
     
     
       16. In a butterfly valve having a valve plate which is pivotally disposed in an elongate flow path defined by a duct, wherein the valve plate is pivotal from a first rotational position maximally closing fluid communication along the path to a second rotational position maximally permitting fluid communication along the path, and wherein the pivotally disposed valve plate is subjected to a net torque exerted thereon by fluid conveyed along the path, a method for exploiting the net torque to facilitate control of the valve, comprising the steps of: rotationally moving the valve plate away from the first position toward the second position whereby the net torque is increased;   translationally moving the valve plate to decrease the net torque, whereby further rotational movement of the valve plate toward the second position is facilitated;   rotationally moving the valve plate further toward the second position, whereby the net torque is again increased; and   translationally moving the valve plate to decrease the again-increased net torque, whereby further rotational movement of the valve plate toward the second position is facilitated.   
     
     
       17. A method as recited in claim 16 wherein the valve plate is rotationally moved to a desired rotational position which is between the first and second positions and is associated with a desired flow rate, and is translationally moved so that at the desired rotational position, the net torque is minimized, whereby maintenance of the valve plate at the desired rotational position is facilitated. 
     
     
       18. The invention of claim 16 wherein the rotational and translational movements collectively form a substantially continuous movement of the valve plate from the first position toward the second position. 
     
     
       19. A method as recited in claim 16 comprising the further steps of: rotationally moving the valve plate away from the second rotational position and toward the first position, whereby the net torque is increased; and   translationally moving the valve plate to again decrease the net torque, whereby further rotational movement toward the first position is facilitated.